The role of a network node is to relay each packet to its destination in a network. Such network nodes are classified roughly into distributed network nodes, integrated network nodes, and “distributed” integrated network nodes. A node receives a packet through its built-in line and searches its destination from the address set in the packet, then transmits the packet to the destination through a line connected to the destination.
FIG. 1 shows a configuration of a distributed network node. The distributed network node (1) consists of a switching module (10) and plural routing and transferring units (11). Each routing and transferring unit 11 is connected to one or more line interface units (12). The distributed network node (architecture) is characterized so that each routing and transferring unit 11, when the distributed network node 1 receives a packet, can search the route of the packet. This means that such packet route searching operations can be distributed.
FIG. 2 shows a configuration of a routing and transferring unit in a distributed network node (architecture) 11. The routing and transferring unit 11 is connected to a processing unit (110) for searching the transfer destination of each packet, an address buffer (111) for storing the information of the destination, a packet transferring unit (112) for transmitting/receiving each packet to/from each line interface unit 12, and a packet buffer (113) for holding received packets. The routing and transferring unit 11 is connected to the switching module 10 and each of the line interface units 12 through the packet transferring unit 112 so as to transmit/receive packets to/from those units 10 and 12.
In the distributed network node 1, each packet received at a port is transferred from a line interface unit 12 to a routing and transferring unit 11. The routing and transferring unit 11 then searches the route of the packet and transfers the packet to the next routing and transferring unit 11 through the switching module 10. The next routing and transferring unit 11, when receiving the packet through the switching module 10, searches the route of the packet and transfers the packet to another line interface unit 12.
An example of such a distributed network node is disposed in the patent document 1. The distributed network node disposed in the patent document 1 reads and transmits information set in plural layers in each packet.
The patent document 2 discloses an example of another distributed network node. The distributed network node disclosed in the patent document 2 includes plural interface cards connected to each another through a single bus and a computing device provided for each of the interface cards. In the distributed network node disclosed in the patent document 2, each interface card searches the route of each received packet. Thus transferring of packets is realized only by an interface controlling means and a transfer controlling means that are both included in the interface card, thereby the load of the CPU that manages the whole network node is reduced.
The distributed network node is characterized so that the more the routing processing is dispersed with use of many routing and transferring units, the more the packet transferring capacity of the network node is improved. This is why the processing speed of the distributed network node can be improved easily by increasing the number of routing and transferring units. FIG. 3 shows a configuration of an integrated network node. This integrated network node (2) includes a single routing and transferring unit 20. The routing and transferring unit 20 is connected to plural line interface units (21). FIG. 4 shows a configuration of a routing and transferring unit 20 of an integrated network node. The routing and transferring unit 20 of the integrated network node includes a processing unit (200), an address buffer (201), a packet transferring unit (202), and a packet buffer (203). The routing and transferring unit 20 is connected to all of the line interface units 21. The routing and transferring unit 20 searches the route of each packet received from the line interface unit 21, then transmits the packet to another line interface unit 21 according to the result of searching. The line interface unit 21, when receiving the packet, transmits the packet through a port according to a command of the routing and transferring unit 20.
An example of such an integrated network node is disclosed in the patent document 3. The patent document 3 also describes some measures for cooling down the integrated network node.
When compared with the distributed network node described above, the integrated network node is not required to connect plural the routing and transferring units to each another with use of a switch, since the integrated network node has only a single searching and transferring unit. Thus the integrated network node can be simple in structure and reduced in size.
Apart from those two types of network nodes described above, there is still another type of network nodes; it is a “distributed” integrated network node. FIG. 5 shows a configuration of the “distributed integrated network node. The “distributed” integrated network node (3) includes plural routing and transferring unit (30) and plural line interface units (31). Each of the routing and transferring unit 30 is connected to one of the line interface units 31 at a one-to-one correspondence. In other words, in the example shown in FIG. 5, each routing and transferring unit 30 is connected to all the line interface units 31 while the routing and transferring units, as well as the line interface units are not connected to each another.
Just like the distributed network node, the “distributed” integrated network node includes plural routing and transferring units. And just like the integrated network node, the “distributed” integrated network node enables each of the routing and transferring units to be connected to each of the line interface units. Because of such a configuration, the “distributed” integrated network node can improve the routing performance with use of the plurality of routing and transferring units and use the processing capacity more effectively by making good use of the connection of each of the routing and transferring units to all the line interface units. When compared with the integrated network node described above, the “distributed” integrated network node can realize high expandability by enabling addition and modification of the routing and transferring units.
There is another example of the “distributed” integrated network node (architecture), which uses a method disposed in the patent document 4. The patent document 4 describes such a “distributed” integrated network node provided with an enhanced processing unit characteristically. FIG. 6 shows a configuration of the network node disclosed in the patent document 4. The “distributed” integrated network node (4) provided with an enhanced packet processing unit includes an enhanced packet processing unit (40), plural routing managers (41) used for routing, and plural line interface units (42) for housing input/output ports that are all connected to each another through a crossbar switch (43). The routing manager 41 has functions for searching the destination interface information of each packet according to the header information set in the packet received from a given line interface unit 42 and transmitting the packet to the line interface unit described in the destination interface information. Furthermore, the line interface unit 42 also has a function for dispersing the load of the routing manager 41. Such a function for dispersing the routing manager's load includes a dividing function that uses a value obtained from a HASH function that assumes a destination IP address in each packet as an input, a circulating selection dividing function added with an order reversing preventive function, and a load dispersing function based on load observation added with an order reversing preventive function.
The network node disclosed in the patent document 4 includes an enhanced packet processing unit 40 and uses different units for different two processings, that is, enhanced packet processing and routing. Consequently, the processing speed of the network node can be much improved when compared with a case in which communications are made between the routing and transferring units.